Iraqi block cipher

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In cryptography, the Iraqi block cipher was a block cipher published in C source code form by anonymous FTP upload around July 1999, and widely distributed on Usenet. It is a five round unbalanced Feistel cipher operating on a 256 bit block with a 160 bit key.

The source code shows that the algorithm operates on blocks of 32 bytes (or 256 bits). That's four times larger than DES or 3DES (8 bytes) and twice as big as Twofish or AES (16 bytes). It also shows that the key size can vary from 160 to 2048 bits.

A detailed analysis of the source code of the algorithm shows that it uses a 256-byte S-Box that is key-dependant (as on Blowfish, it uses a first fixed S table that will generate, with the key, the second S-Box used for encryption/decryption). The algorithm also uses a 16-column x 16-row P-Box, which is also key-dependent and also initialized from a fixed P table. Each round uses one row from P-Box and 16 columns, which means that the algorithm can use up to 16 rounds.

A comment suggests that it is of Iraqi origin. However, like the S-1 block cipher, it is generally regarded as a hoax, although of lesser quality than S-1. Although the comment suggests that it is Iraqi in origin, all comments, variable and function names and printed strings are in English rather than Arabic; the code is fairly inefficient (including some pointless operations), and the cipher's security may be flawed (no proof).

Because it has a constant key schedule the cipher is vulnerable to a slide attack. However, it may take 2⁶⁴ chosen texts to create a single slid pair, which would make the attack unfeasible. It also has many fixed points, although that is not necessarily a problem, except possibly for hashing modes. No public attack is currently available. As with S-1, it was David Wagner who first spotted the security flaws.^[1]

References[edit]

^ David A. Wagner (2000-05-08). "Re: Question about iraqi block cipher". Newsgroup: sci.crypt. Usenet: 8f75u3$jvl$1@blowfish.isaac.cs.berkeley.edu. Retrieved 2008-08-20.

External links[edit]

v t e Block ciphers (security summary)
Common algorithms	AES Blowfish DES (internal mechanics, Triple DES) Serpent SM4 Twofish
Less common algorithms	ARIA Camellia CAST-128 GOST IDEA LEA RC5 RC6 SEED Skipjack TEA XTEA
Other algorithms	3-Way Adiantum Akelarre Anubis Ascon BaseKing BassOmatic BATON BEAR and LION CAST-256 Chiasmus CIKS-1 CIPHERUNICORN-A CIPHERUNICORN-E CLEFIA CMEA Cobra COCONUT98 Crab Cryptomeria/C2 CRYPTON CS-Cipher DEAL DES-X DFC E2 FEAL FEA-M FROG G-DES Grand Cru Hasty Pudding cipher Hierocrypt ICE IDEA NXT Intel Cascade Cipher Iraqi Kalyna KASUMI KeeLoq KHAZAD Khufu and Khafre KN-Cipher Kuznyechik Ladder-DES LOKI (97, 89/91) Lucifer M6 M8 MacGuffin Madryga MAGENTA MARS Mercy MESH MISTY1 MMB MULTI2 MultiSwap New Data Seal NewDES Nimbus NOEKEON NUSH PRESENT Prince Q RC2 REDOC Red Pike S-1 SAFER SAVILLE SC2000 SHACAL SHARK Simon Speck Spectr-H64 Square SXAL/MBAL Threefish Treyfer UES xmx XXTEA Zodiac
Design	Feistel network Key schedule Lai–Massey scheme Product cipher S-box P-box SPN Confusion and diffusion Round Avalanche effect Block size Key size Key whitening (Whitening transformation)
Attack (cryptanalysis)	Brute-force (EFF DES cracker) MITM Biclique attack 3-subset MITM attack Linear (Piling-up lemma) Differential Impossible Truncated Higher-order Differential-linear Distinguishing (Known-key) Integral/Square Boomerang Mod n Related-key Slide Rotational Side-channel Timing Power-monitoring Electromagnetic Acoustic Differential-fault XSL Interpolation Partitioning Rubber-hose Black-bag Davies Rebound Weak key Tau Chi-square Time/memory/data tradeoff
Standardization	AES process CRYPTREC NESSIE
Utilization	Initialization vector Mode of operation Padding

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Mathematics	Cryptographic hash function Block cipher Stream cipher Symmetric-key algorithm Authenticated encryption Public-key cryptography Quantum key distribution Quantum cryptography Post-quantum cryptography Message authentication code Random numbers Steganography
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